Field of the Invention
The present invention relates to an image reading apparatus configured to read images on a sheet, and an image forming apparatus equipped with the same.
Description of the Related Art
Hitherto, Japanese Unexamined Patent Application Publication No. 2013-251692 proposes an image reading apparatus having a sheet conveyance unit provided above an image reading unit, and configured to read an image on a document fed from a sheet conveyance unit through an image reading portion. A transparent member composed of glass or the like is provided on the image reading unit, and the image reading unit is configured to read image information of the document conveyed from the sheet conveyance unit by the image reading portion via the transparent member.
Such image reading apparatus adopts a configuration in which a document passes through a conveyance path clearance (hereinafter referred to as a gap) formed of a sheet guide portion at a lower portion of the sheet conveyance unit and the transparent member at an upper portion of the image reading unit. Therefore, the positioning of the sheet conveyance unit with respect to the image reading unit in a height direction of the sheet conveyance unit and the image reading unit, that is, the vertical direction seen from the front direction of the apparatus, is important. Specifically, the gap between the sheet guide portion and the transparent member is formed by projections projecting from the lower portion of the sheet conveyance unit toward the image reading unit abutting against the transparent member.
Further, Japanese Unexamined Patent Application Publication No. 2011-119920 proposes an image reading apparatus having a first reading portion provided on an image reading unit and configured to read an image on a first surface of a document, and a second reading portion provided on a sheet conveyance unit and configured to read an image on a second surface of the document. The second reading portion is arranged downstream of the first reading portion in the sheet conveyance direction, and the first and second reading portions are configured to read the image on the sheet conveyed through the gap.
If the image reading apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2011-119920 secures the gap by projections abutting against the transparent member provided on the first reading portion side in a way of the image reading apparatus disclosed in Japanese Unexamined Patent Application publication No. 2013-251692, the sheet conveyance unit sinks down at the second reading portion side by its own weight. Thereby, the gap at the reading position of the second reading portion is narrowed, so that conveyance failure of thick paper having a high stiffness or a thin paper having a low stiffness, or image defects in which the image is distorted, may occur.